Force motors having a linearly movable coil for directly driving a servovalve of hydraulic or fluid control systems are illustrated in U.S. Pat. No. 4,530,487 issued Jul. 23, 1985, to Sydney K. Tew and Dan O. Bauer and U.S. Pat. No. 4,560,967 issued Dec. 24, 1985 to Charles T. Lindsey.
A limited angle electric rotary actuator or force motor having a rotating coil around a plurality of inner permanent magnets for positioning a magnetic head of a magnetic disk file relative to information tracks on a disk is shown in U.S. Pat. No. 4,398,167 issued Aug. 9, 1983, to Hugh G. Dickie et al.
A pulse motor having a limited rotational coil disposed around inner permanent magnet for actuating a working element such as a printing cylinder is described in U.S. Pat. No. 4,084,502 issued Apr. 18, 1978, to Marc Heyrand et al.
Commutated electrical force motors are shown in U.S. Pat. No. 3,845,338 issued Oct. 29, 1974, to Mohairam M. Fawzy and U.S. Pat. No. 4,019,075 issued Apr. 19, 1977, to Isao Kagami. The Kagami patent uses a rotary coil with hexagonal windings which is not limited to angular rotation. The Fawzy patent employs a rotatable armature shell on which coils are wound toroidally.
U.S. Pat. No. 4,507,634 issued Mar. 26, 1985, to Robert D. Vanderlean illustrates an electrical force motor with fixed coils and a central rotor assembly including a rotor shaft and permanent magnets thereon within a protective cover to prevent potential rotor magnet breakage contamination. The rotor shaft has an eccentric output shaft. The torque null is adjusted by an eccentric pin engaging the rotor casing, the interior of which as well as rotor assembly therein, is subjected to system hydraulic pressure.